Thursday, October 28, 2021

FROM SAND TO SPAGHETTI: Membrane technology to upgrade Marco water

The first step in water treatment is adding lime. After the lime tank, the water flows into the sand filter, soon to be replaced. SUBMITTED PHOTOS

The first step in water treatment is adding lime. After the lime tank, the water flows into the sand filter, soon to be replaced. SUBMITTED PHOTOS

By Coastal Breeze News Staff 

“Marco is a 100% alternative water source.” Justin Martin’s statement sums up both the challenges and successes dealt to the city’s water utility as it supplies between seven and nine million gallons of fresh water daily to an island surrounded by salt water. When the city took over from Florida Water Services the utility facilities located on Elkcam Circle, it inherited operations equipment built in the 1970’s, now becoming inefficient and obsolete.

Martin, an operations manager, and the rest of the staff have worked to identify and implement new technology suited to the utility’s unique needs. Turbidity is the scientific term for all the solids picked up in water, and since Marco’s water comes mainly from surface runoff, its turbidity can vary widely depending on environmental conditions. The utility currently uses a sand filter due for retirement, and General Manager Jeff Poteet explains, “we’re looking for better, more consistent treatment. If there’s high turbidity going in [to the sand filter] there’s still turbidity going out.”

Enter the new membrane filter expected to come online in October. Instead of a creaky, large, outdoor tank, the water will be pressurized through a series of slender, spaghetti-like fiber-filled tubes, or membranes, now housed indoors. “Only the water molecule can get through the membrane, “adds Poteet.

Martin adds that the department looked at, and rejected, other processing technologies. Settling technology, which traps the particles in water and sinks them, was impractical because of the space and funds needed to buy, store and dispose of settling agents. Ultraviolet technology had high energy costs, explains Martin.

“We visited [membrane technology] in use in Alabama. We’re probably the first

The fibers inside the membrane tube that filter the water.

The fibers inside the membrane tube that filter the water.

plant in Florida to use it, especially on a large scale like this,” says Poteet.

This isn’t the first time the utility has taken the square peg of existing technology and forced it through the round hole of the island’s environmental constraints. The bulk of our water is stored in in ASR, or “bubble” wells, supplied by surface runoff and stored under a lake off of 951. The wells aren’t structures at all, but literally pockets of minimally treated fresh water that forms a natural barrier against the salt water that surrounds it.

“Your average ASR well is small and not economically sustainable,” points out Dr. Bruce Weinstein, a senior project manager with the utility. “Ours are large and require minimal treatment. Now they’re being looked at as a model of economics and sustainability within the industry.”

 

Environmental FYI

Drought eases for East Coast but Southwest Florida still short on rainfall.

South Florida Water Management District has released its July assessment of the rainy season, and coastal Southwest Florida is coming up short, despite the downpours experienced with Tropical Storm Debbiy. 

“Currently, the U.S. Drought Monitor shows South Florida is free from drought conditions, however, the Southwest Coast and Caloosahatchee Basin continued to be classified as abnormally dry, ” states the report. 

“The 2012 wet season began early on May 7, but rainfall totals so far have been tempered by several multi-day dry periods wedged in between heavy downpours and Tropical Storm Debby in June.” 

Technically the rainy season extends into October, but that moisture is variable and dependent on storm systems and cold fronts from this point forward. 

The Southwest Coast, which includes Marco Island, received an average of 17.43 inches of rainfall. 

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